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Last modified
7/14/2009 5:02:34 PM
Creation date
5/22/2009 5:01:43 PM
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UCREFRP
UCREFRP Catalog Number
9319
Author
Mueller, G., M. Horn, Q. Bradwisch and L. Boobar.
Title
Examination of Native Recruitment and Description of the Fish Communities Found in the San Jan and Colorado River Interface Zones of Lake Powell, Utah.
USFW Year
2001.
USFW - Doc Type
01-159,
Copyright Material
NO
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<br />I <br />I <br />I <br />I <br />I <br />I, <br />I <br />I <br />I <br />I <br />I <br />i <br />I <br />I <br />II <br />I <br />I <br />I <br />I <br /> <br />EXECUTIVE SUMMARY <br /> <br />Researchers examined the fish communities of the Colorado and San Juan river interface zones <br />of Lake Powell during 1999 and 2000. The objectives were to: (1) search for young razorback <br />sucker and Colorado pikeminnow and, if found, PIT tag them; (2) examine the effectiveness of <br />various collection techniques on juvenile native fish; and (3) describe the fish communities found <br />in these transitory, or actually "migratory" habitats. The San Juan River interface zone was <br />sampled 5 times each year during the spring and summer while the Colorado River site was <br />sampled a total of 3 times over the 2-year period, all in the spring. <br /> <br />Lake Powell's surface elevation fluctuated 5.3 m during the course ofthe study. Elevational <br />changes caused the reservoir/river interface zone to advance up and retreat down the San Juan <br />River> 15 km. Over 1,000 ha of bottomland at Piute Farms was flooded and drained in 1999 <br />alone. Sampling focused on these migratory habitats. <br /> <br />Nearly 40,000 fish were captured using seines, light traps, electrofishing, minnow traps, fyke <br />nets, and trammel nets. Twenty three species were represented, only 5 species were endemic to <br />the watershed. The fish community was far more indicative of the Mississippi River basin than <br />Colorado River ichthyofauna. Numerically, nonnative fishes dominated the sample (99.4%) <br />while natives only represented 0.6% of the fish collected. Thirteen adult razorback suckers were <br />captured, all believed to be hatchery stocked. No juvenile razorback suckers were found. Three <br />juvenile Colorado pikeminnow and one small chub (Gila spp.) were collected. Flannelmouth <br />sucker was the most common large native species, however, they represented only 0.4% (41) of <br />the fish captured. Two species not previously reported were the white crappie (Promoxis <br />annularis) and gizzard shad (Dorosoma cepedianum). <br /> <br />The most common fish were red shiner, threadfin shad, common carp, striped bass, and channel <br />catfish. Relative abundance was higher at the inflow area compared to a reservoir control site <br />(Spencer' s Camp). Common carp and bullhead sp. were twice as abundant in inflow habitats <br />compared to the reservoir whereas smallmouth bass and green sunfish were less abundant. <br />Species composition and abundance were influenced by habitat availability. For example, adult <br />striped bass and walleye were more common in channel habitat while broad flood plain habitat <br />supported more black crappie and juvenile fish. <br /> <br />Native fish were taken by a variety of sampling methods. No single technique proved effective <br />for a particular species; sampling success was more indicative of life stage. Three species of <br />larval suckers (razorback (2), flannelmouth (3), and possibly bluehead (2)) were captured in light <br />traps. A juvenile Gila spp. and three juvenile Colorado pikeminnow were captured by minnow <br />trap, seine, and trammel net, respectively. The majority of adult flannelmouth (36 or 86%) and <br />razorback suckers (11 or 92%) were taken by trammel net. However, two (8%) razorback sucker <br />were captured by electrofishing and 5 (14%) flannelmouth suckers were taken by hoop net. <br /> <br />v <br />
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